Generally, a head gimbal assembly in a hard disc drive extends from a rotatable actuator arm and includes a load beam supporting a slider that flies parallel to a rotating storage disc surface. The slider typically contains one or more writers for writing data to the storage disc and one or more read sensors for retrieving data from the storage disc. The actuator arm and head gimbal assembly rotate about an actuator motor to align with individual radially-positioned target data tracks for reading and writing operations.
Among other control structures and circuitry, the actuator arm and head gimbal assembly operate to align the one or more read sensors and/or one or more write poles with a target data track. During rotation at high speeds, however, the storage disc can bend (e.g., up and down relative to the horizontal rotating plane) in a manner that is referred to as “disc flutter.” Disc flutter can cause the slider to lose radial alignment with a target data track—the load beam supporting the slider bends to allow the slider to remain in close proximity to storage disc surface as storage disc flutters, but the slider also moves radially in and out relative to the center of the storage disc as the storage disc flutters. Such radial movement of the slider relative to the target data track can result in slider misalignment with the target data track, which is referred to as track mis-registration (TMR).